Contingencies and Gain on Sale of Assets (Details)		6 Months Ended
	Jun. 08, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Proceeds from sale of assets		$ 29,000	$ 34,324,000
Amount spent in clean-up and remediation activities [Abstract]		1,500,000
Utility plant		1,238,789,000	1,155,203,000	$ 1,204,992,000
Accounts receivable		26,631,000		26,127,000
Total Assets		1,441,122,000	1,462,653,000	1,416,734,000
Advances for construction		(66,761,000)		(67,465,000)
Contributions in aid of construction - net		123,950,000		123,602,000
GOLDEN STATE WATER COMPANY
Loss Contingencies [Line Items]
Environmental Remediation Expense		5,500,000
Proceeds from sale of assets		0	34,324,000
Utility plant		1,227,371,000		1,197,940,000
Accounts receivable		26,631,000		26,127,000
Regulatory assets		(10,799,000)		2,042,000
Total Assets		1,341,075,000		1,326,823,000
Advances for construction		(66,761,000)		(67,465,000)
Contributions in aid of construction - net		123,950,000		$ 123,602,000
Environmental Clean-Up and Remediation | GOLDEN STATE WATER COMPANY
Loss Contingencies [Line Items]
Accrued liability for the estimated additional cost to complete the clean-up at the site		$ 1,300,000
Ojai Water System
Loss Contingencies [Line Items]
Loss contingency number of customers served	2,900
Ojai Water System | GOLDEN STATE WATER COMPANY
Loss Contingencies [Line Items]
Proceeds from sale of assets	$ 34,300,000
Gain (loss) on sale of properties			$ 8,300,000